distanceFromLocation - 计算两点之间的距离

Question

只是一个关于核心位置的快速问题，我正在尝试计算两点之间的距离，代码如下：

    -(void)locationChange:(CLLocation *)newLocation:(CLLocation *)oldLocation
    {   

    // Configure the new event with information from the location.
        CLLocationCoordinate2D newCoordinate = [newLocation coordinate];
        CLLocationCoordinate2D oldCoordinate = [oldLocation coordinate];

        CLLocationDistance kilometers = [newCoordinate distanceFromLocation:oldCoordinate] / 1000; // Error ocurring here.
        CLLocationDistance meters = [newCoordinate distanceFromLocation:oldCoordinate]; // Error ocurring here.
}

我在最后两行收到以下错误：

错误：无法转换为指针类型

我一直在谷歌上搜索，但找不到任何东西。

Answer 1

试试这个：

CLLocationDistance meters = [newLocation distanceFromLocation:oldLocation];

您尝试使用的方法是 CLLocation 对象上的方法 :)

Answer 2

#import <CoreLocation/CoreLocation.h>

CLLocation *locA = [[CLLocation alloc] initWithLatitude:"Value" longitude:"Value"];

CLLocation *locB = [[CLLocation alloc] initWithLatitude:"Value" longitude:"Value"];

CLLocationDistance distance = [locA distanceFromLocation:locB];
NSLog(@"distance:-%f",distance);//distance in Miter

Answer 3

距离是计算 2 个 CLLocations 之间的距离，而不是坐标之间的距离。

您需要使用这些坐标获取相应坐标的 CLLocations，使用以下代码行

CLLocation *newLocation = [[CLLocation alloc] initWithCoordinate: newCoordinate altitude:1 horizontalAccuracy:1 verticalAccuracy:-1 timestamp:nil];

对于另一个坐标也是如此，然后您可以使用以下代码行计算这两个位置之间的距离

CLLocationDistance kilometers = [newLocation distanceFromLocation:oldLocation] / 1000;

希望这会对你有所帮助。

更新： Swift 3.0

let distanceKiloMeters = (newLocation.distance(from: oldLocation))/1000

Answer 4

在 Swift 中

让我们创建一个计算两个位置之间距离的方法函数：

 func distanceBetweenTwoLocations(source:CLLocation,destination:CLLocation) -> Double{

        var distanceMeters = source.distanceFromLocation(destination)
        var distanceKM = distanceMeters / 1000
        let roundedTwoDigit = distanceKM.roundedTwoDigit
        return roundedTwoDigit

    }

如果你只想要两个数字：

extension Double{

    var roundedTwoDigit:Double{

        return Double(round(100*self)/100)

        }
    }

Answer 5

如果您打算使用 2 个 CLLocationCoordinate2D 值，那么您可以使用它。

这是 Xcode 7.1 上的 Swift 2.1

import CoreLocation

extension CLLocationCoordinate2D {

    func distanceInMetersFrom(otherCoord : CLLocationCoordinate2D) -> CLLocationDistance {
        let firstLoc = CLLocation(latitude: self.latitude, longitude: self.longitude)
        let secondLoc = CLLocation(latitude: otherCoord.latitude, longitude: otherCoord.longitude)
        return firstLoc.distanceFromLocation(secondLoc)
    }

}

Answer 6

取自优秀的库CoreLocation utitlities：

- (CLLocationDistance) distanceFromCoordinate:(CLLocationCoordinate2D) fromCoord;
{
    double earthRadius = 6371.01; // Earth's radius in Kilometers

    // Get the difference between our two points then convert the difference into radians
    double nDLat = (fromCoord.latitude - self.coordinate.latitude) * kDegreesToRadians;  
    double nDLon = (fromCoord.longitude - self.coordinate.longitude) * kDegreesToRadians; 

    double fromLat =  self.coordinate.latitude * kDegreesToRadians;
    double toLat =  fromCoord.latitude * kDegreesToRadians;

    double nA = pow ( sin(nDLat/2), 2 ) + cos(fromLat) * cos(toLat) * pow ( sin(nDLon/2), 2 );

    double nC = 2 * atan2( sqrt(nA), sqrt( 1 - nA ));
    double nD = earthRadius * nC;

    return nD * 1000; // Return our calculated distance in meters
}

Answer 7

这里的问题是你正在调用一个对象method：

- (CLLocationDistance)distanceFromLocation:(const CLLocation *)location;

属于 CLLocation 类。

CLLocationCoordinate2D 实际上是一个结构，由两个双精度组成：

typedef struct
{
    CLLocationDegrees latitude;
    CLLocationDegrees longitude;
} CLLocationCoordinate2D;

这样做的正确方法是获取一个CLLocation 对象并在其上调用distanceFromLocation。像这样：

CLLocation* newLocation;
CLLocation* oldLocation;
CLLocationDistance distance = [newLocation distanceFromLocation:oldLocation];

当然，您首先需要初始化这两个值（例如，来自CLLocationManager）。